1. Field of the Invention
The present invention relates to a video camera system to be preferably applied to a video camera having, for example, an automatic exposure (AE) adjusting function, an automatic tracing white-balance (ATW) adjusting function, and/or an automatic contrast (AK: Automatic Knee) adjusting function.
2. Description of the Related Art
Conventional automatic adjusting functions of a video camera include an automatic exposure adjusting function for automatically adjusting an exposed state to an optimum state, an automatic tracing white-balance adjusting function for automatically adjusting a white balance to an optimum state, and an automatic contrast adjusting function for automatically adjusting a contrast of a picture to an optimum state.
In this case, automatic exposure adjustment is performed by successively detecting the peak value or average value of image pickup outputs of an image pickup device for, for example, one field period and controlling the iris of an optical system so that the peak value or average value becomes equal to a preset threshold or less.
Moreover, automatic tracing white-balance adjustment is performed by obtaining the integrated value of each primary color signal for, for example, one frame period and controlling the gain of a white-balance amplifier so that the ratio of red-signal integrated value IR to green-signal integrated value IG (IR/IG) and the ratio of blue-signal integrated value IB to green-signal integrated value IG (IB/IG) always meet the following expression (that is, IR:IG:IB=1:1:1).                               IR          IG                =                              IB            IG                    =          1                                    (        1        )            
Moreover, automatic contrast adjustment (auto-knee) is performed by detecting the peak value of intensity levels for, for example, one field period and varying so-called knee points P1 and P2 which are reference levels for starting the compression processing (knee processing) of a high-intensity component so that the peak value does not exceed a clip level CL as shown in FIG. 1.
A conventional video camera having various automatic adjustment functions such as the above automatic exposure adjusting function, automatic tracing white-balance adjusting function, and automatic contrast adjusting function temporarily stores video data for one frame in a frame memory so as to detect or compute control information necessary to perform various kinds of automatic adjustment processing in accordance with the video data stored in the frame memory. Therefore, this type of video camera has problems that the circuit size increases because a frame memory is necessary and thereby, it is difficult to decrease the camera in size and weight.
Moreover, to disuse a frame memory, the official gazette of Japanese Patent Application Laid-Open No. 276976/1991 discloses a method of dividing a frame screen into a plurality of regions (hereafter referred to as divided regions), simultaneously detecting the maximum value of the video data for each divided region in the same frame period by a plurality of detection circuits, and detecting or computing control information necessary to perform various kinds of automatic adjustment processing in accordance with the detection results.
However, this method has problems that a circuit for simultaneously detecting the maximum value of video data in each divided region is necessary and thereby, the circuit size increases.
In view of the foregoing, an object of this invention is to provide a video camera system having a simplified structure.
The foregoing objects and other objects of the invention have been achieved by the provision of a video camera system comprising information-obtaining-region setting means for setting an information-obtaining region in a screen in accordance with the output of an image pickup device, information-obtaining-region moving means for moving an information-obtaining region in the screen every predetermined cycle of the output of the image pickup device, information-obtaining means for obtaining predetermined obtained-region information based on the output of the image pickup device in an information-obtaining region every predetermined cycle, and control-information generating means for generating control information in accordance with the obtained-region information obtained by the information-obtaining means.
As a result, the video camera system can omit a frame memory for obtaining control information from the output of an image pickup device and a circuit for simultaneously detecting the maximum value of video data from each divided region when obtaining control information by dividing a screen and simultaneously detecting the maximum value of the video data from each divided region.
The nature, principle and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings in which like parts are designated by like reference numerals or characters.